The present invention relates generally to power monitoring systems and, more particularly, to impulsive transient simulation for use in a power monitoring system.
Power monitoring (PMO) systems monitor the flow of electrical power in circuits through a plant or other facility. In the POWERLOGIC system manufactured by the instant assignee, circuit monitors and power meters are dedicated to power monitoring, while other compatible devices collect additional equipment information from protective relays, circuit breakers, transformer temperature controllers, and panelboards. Electrical data, such as current, power, energy, waveforms, and equipment status, is passed over a data network to one or more personal computers. The personal computers run power monitoring application software that retrieves, stores, organizes, and displays real-time circuit information in simple, usable formats. The information collected and stored in a power monitoring system helps operate a facility more efficiently. The quality of the data depends upon the accuracy of the instrumentation and the usability of the display formats.
The power meter can replace conventional metering devices such as ammeters, voltmeters, and watt-hour meters while providing other capabilities not offered by analog metering. The power meter""s true rms readings reflect non-linear circuit loading more than conventional analog metering devices. The power meter calculates the neutral current, which can assist in identifying overloaded neutrals due to either unbalanced single phase loads or triplen harmonics. Circuits can be closely monitored for available capacity by keeping track of the peak average demand current.
The power meter can provide a full complement of rms metering values to a metering display and/or via a standard communication port to a power monitoring and control system. The display is connected to the power meter with a communications cable and allows the user to view metering data and access meter setup and reset menus. Because the display can be mounted at a remote location relative to the power meter itself, the power meter can be installed in tight equipment spaces without sacrificing a convenient and affordable metering display.
One type of remote metering display includes a character-based display screen that presents power monitoring data such as voltage, current, power and energy. The display is remote from the power meter but is connected to the power meter via an RS-232 or other communications cable that provides both the power metering data and power to the display. By using several user interface buttons, a user can selectively navigate through defined data screens that present specific data. The remote metering display may be mounted on a front switchgear panel while the power meter itself is mounted within the switchgear. In fact, there may be several displays mounted on the same front switchgear panel.
High voltage transients can degrade power systems. The high data rates required in transient detection are too fast for the microprocessors in current PMO products to handle by themselves and still perform other data sampling and reporting functions at the desired rate. The occurrence of these transients is often intermittent and unpredictable.
A Transient-Current-Voltage (TCV) Module of the type described in copending U.S. patent application Ser. No. 09/824,414, filed Apr. 2, 2001 solves the problem of unattended detection, storage, and analysis of these transients. The Acquire/Trigger/Control/Interface (ATCI) chip is a component of the TCV and makes the TCV possible. When used in a system with a general purpose microprocessor, the ATCI chip makes possible the continuous real-time detection and storage of high voltage transients on any of three independent channels. The xe2x80x9cplug-inxe2x80x9d nature of the module makes it easy for the customer to upgrade an existing PMO, such as a current-voltage monitor (CVM) with a TCV by simply replacing the module and downloading the main meter firmware.
Square D, the assignee, currently manufactures a CVM, known as a CM4 meter. This invention adds transient analysis capability to an existing CM4 meter in a small, relatively low cost plug-in module and enhances the functionality of the CM4. It allows the customer to add transient analysis to the CM4 by simply purchasing the module and upgrading the CM4 firmware. It provides transient analysis capability to customers at significantly lower cost than competitive offerings. The CM4 can analyze data at a rate of 512 samples/cycle. The TCV can analyze data at a rate of 83,333 samples/cycle. Any customer who wants high speed transient analysis in addition to the present low speed analysis can use the TCV.
All PMO products must be tested before shipment to assure that they are operating. Normally, this is done with external test equipment. Although external test equipment may still be necessary to assure the product work after it is manufactured, this invention enhances the normal manufacturing test and carries testing a step farther. In accordance with the invention, if an unobtrusive signal source is included at the very beginning of the signal path of an analog measurement system, high confidence in the functionality of the entire measurement system can be obtained by injecting test signals using the signal source and verifying the system response.
Briefly, in accordance with the foregoing, an on-board self test system for an electrical power monitoring device comprises a test signal circuit in an electronic circuit of the monitoring device, and responsive to a programmable test input signal for producing an analog signal simulating an electrical power waveform, and programmable memory in an electronic circuit of the monitoring device and operatively coupled with the test signal circuit for storing and reproducing upon command, one or more of the programmable test input signals.
In accordance with another aspect of the invention, a self test method for an electrical power monitoring device comprises generating a test signal in an electronic circuit of the monitoring device in response to a programmable test input signal, and storing and reproducing upon command in an electronic circuit of the monitoring device one or more of the programmable test input signals.
In accordance with another aspect of the invention, a self test system for an electrical power monitoring device comprising means for generating a test signal in an electronic circuit of the monitoring device in response to a programmable test input signal; and means for storing and reproducing upon command in an electronic circuit of said monitoring device one or more of the programmable test input signals.